The invention relates to an injection head for a corrugator for the production of plastics pipes, with a main head having at least one connection for a plastics extruder, with a nozzle body which is attached to the main head so as to be in axial alignment and with at least one mouthpiece which is attached to the nozzle body so as to be in axial alignment and has an output annular slot for the corresponding plastics material, the at least one mouthpiece having a central body and a sleeve body surrounding said central body which determine the associated output annular slot.
Injection heads of this type are known for example from U.S. Pat. No. 3,743,456, EP 0 208 055 A1, EP 0 230 055 A1 or DE 2 911 833 C2. They are used for example for the production of transverse ribbed pipes made of a single plastics material or for the production of transverse ribbed pipes made of different plastics materials. Plastics pipes of the latter type can have for example a smooth inner layer made of a plastics material and a corrugated outer layer which is integrally connected to said inner layer and is made of the same plastics material or a second plastics material differing therefrom.
In the case of known injection heads of the generic type for the production of plastics pipes, in particular transverse ribbed pipes, consisting of a smooth inner layer and a corrugated outer layer, the nozzle body has for the outer layer an outer sleeve element and an inner sleeve element set radially apart therefrom and for the inner layer an outer sleeve element and an inner sleeve element set radially apart therefrom. The nozzle body of known injection heads of the generic type therefore consists of a corresponding number of individual parts; this affects the manufacturing costs of known injection heads. The same applies to the main head of the known injection heads. A further defect of known injection heads of the generic type consists in the fact that the at least one mouthpiece, which is attached to the nozzle body at the front, requires spacer rings for precise centering thereof, and that there is also a need, between the central body and the sleeve body of the mouthpiece that surrounds said central body, for centering pins which impede the flow of the melted plastics material, so that striation in the melted plastics material issuing from the output annular slot is often inevitable. A very basic defect of known injection heads of the generic type consists in the fact that changing the injection head for the production of plastics pipes having a desired different diameter is time-consuming, i.e. the exchanging times are relatively long.